3. You never changed lenses, nor zoomed the one lens you left on the camera.

2. You never shoot any aperture smaller than f/2. Shallow DOF rulez!

1. You never used it: guarantee to never see dust spots if your camera stays in the box!

For the record, seriously, previous D90 owner here. Used it mostly for landscapes at f/11, and yes, I had to clean it several times. Was it ever as bad as my D600 has been the first 300 actuations? No. But saying it is dust free or claiming dust is not an issue with it is hard to accept with a straight face.